Cells and batteries based on metals such as those having an alkali metal anode (negative electrode) and finely divided metal oxide cathode (positive electrode) are known. Particularly favored are such cells comprising a lithium foil anode active material of a thickness of about 75 microns, or a composite intercalation anode layer of the same thickness; and an intercalation cathode layer of a similar thickness which contains finely divided transition metal oxide active material, electrically conductive carbon and solid electrolyte material. An electrolyte layer having a thickness of about 25 microns is positioned between the anode and cathode and often comprises an ion conducting polymer such as polyethylene oxide complexed with an ionizable alkali metal, preferably, lithium salt. The electrolyte layer separates the anode and cathode from one another while providing transport of ions between the anode and cathode. Typically, a current collector of conductive metal is positioned on the sides of both of the electrodes away from the electrolyte layer.
The cathode (positive electrode) provides for storage of lithium ions released from the anode (negative electrode) during discharge of the battery. Such ions are releasably retained by the cathode and then are transported back to the anode during charge. The cathode is a composite of ionically and electrically conductive materials disposed between the electrolyte layer and cathode current collector plate to provide the necessary transport between such components of the cell. The composite cathode should have a high solid and active material content and good mechanical strength. This is very difficult to achieve. There are two interfaces on the cathode side of the cell, the electrolyte-cathode interface and the cathode-current collector interface. It is difficult to achieve good contact between the cathode material and the cathode current collector. Failure to achieve good contact leads to an overall increase in cell impedance and makes it difficult to recharge the cell.
It is desirable to increase the solid, active material content of the composite cathode and to enhance contact between the composite cathode material and the current collector.
It is also desirable to have a cost-effective and convenient method for manufacturing cells and batteries which reduces waste and unnecessary thickness of the cathode layer, and particularly the composite cathode material.